When a famous painting by artist Johannes Vermeer is stolen, two sixth-graders, Petra and Calder, find themselves drawn into the mystery. Using their unique talents—Petra's curiosity about art and Calder's love for puzzles—they follow a trail of strange coincidences and coded messages in their Chicago neighborhood. As they investigate, they discover that art theft is more dangerous than they imagined, and they must learn to trust their intuition and friendship to solve the case before it's too late.